Curable composition and its cured product

Abstract

To provide a curable composition exhibiting high storage stability and its cured product.SOLUTION: There is provided a curable composition which comprises a cyclic silanol (A1) represented by formula (1) (wherein, R is independently a fluorine atom, an aryl group, an alkenyl group, a fluorine-substituted straight-chain or branched alkyl group having 1 to 4 carbon atoms or an unsubstituted straight-chain or branched alkyl group having 1 to 4 carbon atoms, n is an integer of 2 to 10) and optionally a dehydration condensate (A2) of the cyclic silanol (A1), wherein a solution of the curable composition, in which the total amount of the cyclic silanol (A1) and the dehydration condensate (A2) is 10 mass%, is measured in a quartz cell with a path length of 10 mm and the average transmittance of light at wavelengths of 265 nm to 320 nm is 75% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a curable composition and a cured product thereof. [Background technology]

[0002] Cyclic silanols are compounds having a skeleton in which a cyclic structure is formed by siloxane bonds, and curable compositions containing such compounds have industrial applicability in the fields of protection, sealing, and adhesion of semiconductor elements such as light-emitting diode elements, changing or adjusting the wavelength of light emitted from light-emitting diode elements, lenses, etc. Furthermore, the silanol cured product of the present invention has industrial applicability in the fields of various optical materials such as lens materials, optical devices, materials for optical components, and display materials, electronic devices, insulating materials for electronic components, coating materials, etc.

[0003] In recent years, a curable composition containing tetrahydroxytetramethyltetracyclosiloxane that has transparency due to precise control of the structure has been disclosed (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-105475 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the curable composition disclosed in the examples of Patent Document 1, polymerization of cyclic silanols proceeds during storage after preparation, and therefore improvement in storage stability is required.

[0006] Therefore, an object of the present invention is to provide a curable composition that exhibits high storage stability, and a cured product thereof. [Means for solving the problem]

[0007] As a result of intensive research to solve the above problems, the inventors have found that the storage stability of a curable composition can be improved by adjusting the transmittance of light having a wavelength of 265 nm to 320 nm to a predetermined value or more, and have completed the present invention.

[0008] <1> Formula (1): [ka] (in formula (1), each R independently represents a fluorine atom, an aryl group, an alkenyl group, a linear or branched alkyl group having 1 to 4 carbon atoms and substituted with fluorine, or an unsubstituted linear or branched alkyl group having 1 to 4 carbon atoms, and n is an integer of 2 to 10), and optionally a dehydration condensate (A2) of the cyclic silanol (A1), A curable composition having an average transmittance of 75% or more for light having a wavelength of 265 nm to 320 nm when a solution of the curable composition in which the total amount of the cyclic silanol (A1) and the dehydration condensate (A2) is 10 mass % is measured in a quartz cell having an optical path length of 10 mm. <2> The cyclic silanol (A1) is Equation (10): [ka] (in formula (10), R has the same meaning as R in formula (1)), <1> The curable composition according to claim 1. <3> The cyclic silanol (A10) is Equations (2)~(5): [ka] [ka] [ka] [Chemical formula] It contains cyclic silanols (B1) to (B4) represented by (in formulas (2) to (5), R has the same meaning as R in the above formula (1)). The curable composition according to <2>, where when the ratio (mol%) of the cyclic silanol (B2) to the total amount of the cyclic silanols (B1) to (B4) is b, 0 < b ≤ 20 is satisfied. <4> The curable composition according to any one of <1> to <3>, which contains a dehydrated condensate (A2) of the cyclic silanol (A1). <5> In the peak of the chromatogram obtained by measurement of gel permeation chromatography, the area ratio of the dehydrated condensate (A2) to the total area of the cyclic silanol (A1) and the dehydrated condensate (A2) is 50% or less. The curable composition according to any one of <1> to <4>. <6> The curable composition according to any one of <1> to <5>, which contains the cyclic silanol (A1) represented by the above formula (1) and its dehydrated condensate (A2) at a concentration of 1% to 99% by mass. <7> The curable composition according to any one of <1> to <6>, where the transmittance with respect to light of at least one wavelength selected from the group consisting of wavelengths 265 nm, 280 nm, and 320 nm is 70% or more. <8> A cured product of the curable composition according to any one of <1> to <7>, The cured product has a transmittance of 70% or more with respect to light of at least one wavelength selected from the group consisting of wavelengths 265 nm, 280 nm, and 320 nm at a thickness of 500 μm. <9> The cured product according to <8>, where the transmittance with respect to light of at least one wavelength selected from the group consisting of wavelengths 265 nm, 280 nm, and 320 nm at a thickness of 500 μm is 80% or more. <10> <1> ~ <7> The curable composition according to any one of the above, <8> or <9> An optical material for ultraviolet radiation, which is the cured product according to claim 1. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a curable composition that exhibits high storage stability, and a cured product thereof. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 shows the 1H-NMR spectrum used to calculate the stereoisomer ratio of the curable composition obtained in Example 1. [Figure 2] FIG. 2 shows the 1H-NMR spectrum used to calculate the stereoisomer ratio of the curable composition obtained in Example 2. [Figure 3] FIG. 3 shows the 1H-NMR spectrum used to calculate the stereoisomer ratio of the curable composition obtained in Comparative Example 1. [Figure 4] FIG. 4 is a photograph showing the surface condition of the cured product of the curable composition obtained in Example 1 after storage. [Figure 5] FIG. 5 is a photograph showing the surface condition of the cured product of the curable composition obtained in Example 2 after storage. [Figure 6] FIG. 6 is a photograph showing the surface condition of the cured product of the curable composition obtained in Comparative Example 1 after storage. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a mode for carrying out the present invention (hereinafter also referred to as "the present embodiment") will be described in detail. Note that the present invention is not limited to the present embodiment, and various modifications can be made within the scope of the gist of the present invention.

[0012] [Curable composition] The curable composition according to this embodiment is Formula (1): [ka] (in formula (1), each R independently represents a fluorine atom, an aryl group, an alkenyl group, a linear or branched alkyl group having 1 to 4 carbon atoms and substituted with fluorine, or an unsubstituted linear or branched alkyl group having 1 to 4 carbon atoms, and n is an integer of 2 to 10), and optionally a dehydration condensate (A2) of the cyclic silanol (A1), A solution of the curable composition containing the cyclic silanol (A1) and the dehydration condensate (A2) in a total amount of 10 mass % is measured in a quartz cell with an optical path length of 10 mm, and the average transmittance of light with a wavelength of 265 nm to 320 nm is 75% or more. According to the above-mentioned configuration, it is possible to provide a curable composition exhibiting high storage stability and a cured product thereof.

[0013] The average transmittance of light having a wavelength of 265 nm to 320 nm is preferably 80% or more, and more preferably 85% or more. The transmittance of light having a wavelength of 265 nm to 320 nm may be 99% or less. The average transmittance is measured by the method described in the examples.

[0014] The transmittance of the film with respect to at least one light wavelength selected from the group consisting of 265 nm, 280 nm, and 320 nm is preferably 60% or more, more preferably 70% or more, and may be 99% or less.

[0015] The transmittance for light with a wavelength of 265 nm is preferably 55% or more, more preferably 60% or more, even more preferably 70% or more, and still more preferably 80% or more. There is no particular upper limit to the transmittance for light with a wavelength of 265 nm, but it may be, for example, 99% or less.

[0016] The transmittance for light with a wavelength of 280 nm is preferably 55% or more, more preferably 60% or more, even more preferably 70% or more, and even more preferably 80% or more. There is no particular upper limit to the transmittance for light with a wavelength of 280 nm, but it may be, for example, 99% or less.

[0017] The transmittance for light with a wavelength of 320 nm is preferably 55% or more, more preferably 60% or more, even more preferably 70% or more, still more preferably 80% or more, and still more preferably 90% or more. There is no particular upper limit to the transmittance for light with a wavelength of 320 nm, but it may be, for example, 99% or less.

[0018] Here, the transmittance of the curable composition is a value measured by measuring a solution of the curable composition containing 10% by mass of the cyclic silanol (A1) and the dehydration condensate (A2) in a quartz cell with an optical path length of 10 mm, using the cyclic silanol (A1) and the dehydration condensate (A2) of the solution as a blank and the solvent as a background. More detailed measurement methods are as described in the Examples. The solution used for measurement is an isopropanol solution containing less than 5 ppm of a volatile substance that absorbs light at wavelengths of 265 nm to 320 nm. The volatile substance is a substance, such as toluene, whose boiling point at normal pressure is 150°C or less.

[0019] The increase Δ% in the proportion (%) of the cyclic silanol (A2) relative to the total amount of the cyclic silanol (A1) and the dehydration condensate (A2) in the curable composition after standing at 25°C for 48 hours is preferably 10% or less, more preferably 8% or less.

[0020] Here, the above-mentioned Δ% in the curable composition is an evaluation of storage stability indicated by the difference in the proportion (%) of cyclic silanol (A2) before and after leaving a solution of the curable composition, in which the total amount of cyclic silanol (A1) and dehydration condensate (A2) is 10% by mass, at 25°C for 48 hours, and the increase in the proportion is a value calculated by gel permeation chromatography (GPC) measurement. More detailed measurement methods are described in the Examples.

[0021] By purifying the cellulose used in purifying the curable composition before use, it is possible to obtain a curable composition having a transmittance within the above range. Details of the purification method will be described later.

[0022] (cured product) The cured product according to this embodiment is a cured product of the curable composition according to this embodiment, and has a transmittance of 70% or more at a thickness of 500 μm for light of at least one wavelength selected from the group consisting of 265 nm, 280 nm, and 320 nm. The transmittance of the cured product according to this embodiment is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more.

[0023] Here, the transmittance of the cured product is the value converted into the transmittance value for a thickness of 500 μm. More detailed measurement methods are according to the methods described in the examples.

[0024] By purifying the cellulose used in purifying the curable composition before use, a curable composition having transmittance and storage stability within the above-mentioned ranges can be obtained. Furthermore, even after 48 hours at 25°C, a cured product with a smooth surface can be obtained. Details of this purification method will be described later.

[0025] The cured product according to this embodiment is a cured product of the curable composition according to this embodiment. The cured product according to this embodiment is obtained by curing, i.e., by forming siloxane bonds (-Si-O-Si-) through a dehydration condensation reaction of silanol groups (-Si-OH) contained in the curable composition according to this embodiment. The cured product according to this embodiment is insoluble in solvents such as tetrahydrofuran and toluene.

[0026] The cured product is a curable composition containing a cyclic silanol (A1) represented by the following formula (1). Therefore, when used as a lens material for a light-emitting element such as a UV-LED, for example, it can provide high output at a specific wavelength from the light-emitting element, and also has the effect of preventing cracks from occurring during molding or curing.

[0027] [ka]

[0028] In formula (1), each R is independently fluorine, an aryl group, an alkenyl group, a linear or branched alkyl group having 1 to 4 carbon atoms and substituted with fluorine, or an unsubstituted linear or branched alkyl group having 1 to 4 carbon atoms.

[0029] Examples of the aryl group include a phenyl group and a naphthyl group.

[0030] Examples of the alkenyl group include a vinyl group, an allyl group, a butadienyl group, a hexatrienyl group, and an octatetraenyl group.

[0031] Examples of the fluorine-substituted linear or branched alkyl having 1 to 4 carbon atoms include the following groups. CF3-, CF3CF2-, CF3CF2CF2-, (CF3)2CF-, CF3CF2CF2CF2-, HCF2CF2CF2CF2-, (CF3)2CFCF2-

[0032] Examples of the unsubstituted linear or branched alkyl having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and tert-butyl.

[0033] In formula (1), each R is preferably an unsubstituted, linear or branched alkyl group having 1 to 4 carbon atoms.

[0034] In the curable composition according to this embodiment, the wavelength of transmitted UV light can be controlled by the structure of R. The structure of an unsubstituted or fluorine-substituted alkyl group having 1 to 4 carbon atoms has almost no absorption in the 265 to 320 nm wavelength range due to the absence of unsaturated bonds. Therefore, from the viewpoint of transmitting light with wavelengths of 265, 280, and 320 nm, the R group is preferably an unsubstituted or fluorine-substituted linear alkyl group having 1 to 4 carbon atoms. From the viewpoint of transmitting light with wavelengths of 280 and 320 nm, R is preferably an alkenyl group such as a hexatrienyl group, and from the viewpoint of transmitting light with wavelengths of 320 nm, R is preferably an aryl group such as a phenyl group.

[0035] The cyclic silanol (A1) preferably contains a cyclic silanol (A10) represented by formula (10). [ka] (In formula (10), R has the same meaning as R in formula (1).) The curable composition according to this embodiment contains the cyclic silanol (A10) represented by formula (10), and thus has excellent crack resistance and transparency.

[0036] The cyclic silanol (A10) is Equations (2)~(5): [ka] [ka] [ka] [ka] (In the formulas (2) to (5), R has the same meaning as R in the formula (1) above.) When the ratio (mol%) of cyclic silanol (B2) to the total amount of cyclic silanols (B1) to (B4) is b, it is preferable that 0 < b ≤ 20. By satisfying this range, the transmittance for at least one wavelength selected from the group consisting of wavelengths of 265 nm, 280 nm, and 320 nm can be further improved. Further, from the same viewpoint, it is more preferable for the curable composition to satisfy 0 < b ≤ 15, and still more preferable to satisfy 0 < b ≤ 13.

[0037] The curable composition according to the present embodiment may contain a dehydration condensate (A2) of a cyclic silanol (A1) represented by formula (1). The dehydration condensate (A2) of the cyclic silanol (A) represented by formula (1) is a compound obtained by a reaction in which at least one of the silanol groups of the cyclic silanol (A1) represented by formula (1) is at least one cyclic silanol (A1) represented by formula (1) and undergoes dehydration condensation with at least one silanol group in another cyclic silanol molecule to form a siloxane bond. The dehydration condensate (A2) of the cyclic silanol (A1) represented by formula (1) can be schematically represented, for example, by the following formula (7).

[0038]

Chemical formula

[0039] In formula (7), R has the same definition as R in formula (1), and m is a number of 2 or more. The silanol group that undergoes dehydration condensation in the cyclic silanol may be any silanol group. At this time, in the dehydration condensate represented by formula (7), two or more siloxane bonds may be formed between two or more cyclic silanol structures. Further, examples of the preferable groups of R in formula (7) may include the same preferable groups as R in formula (1).

[0040] Specific examples of the dehydration condensation product (A2) of the cyclic silanol (A1) represented by formula (1) include the following compounds, however, the dehydration condensation product (A2) of the cyclic silanol (A1) represented by formula (1) is not limited to the following compounds.

[0041] In the following compounds, the orientation of the hydroxy group (—OH) and the R group relative to the cyclic silanol skeleton is not limited.

[0042] [ka]

[0043] [ka]

[0044] [ka]

[0045] [ka]

[0046] [ka]

[0047] The dehydration condensate (A2) of the cyclic silanol (A1) represented by formula (1) preferably has a weight average molecular weight calculated by gel permeation chromatography measurement of 500 to 1,000,000, more preferably 500 to 100,000, and even more preferably 500 to 10,000.

[0048] In the curable composition according to this embodiment, the area ratio of the dehydration condensate (A2) to the total area of ​​the cyclic silanol (A1) and the dehydration condensate (A2) (hereinafter also referred to as the "area ratio of A2") is preferably 50% or less in gel permeation chromatography measurement. The area ratio is calculated from [A2] / [[A1]+[A2]]×100 (where [A1] is the area of ​​the cyclic silanol (A1), and [A2] is the area of ​​the dehydration condensate (A2)). The area of ​​each compound determined by gel permeation chromatography measurement represents the content of each compound in the curable composition.

[0049] When the area ratio of A2 is 50% or less, the viscosity does not become too high when the curable composition is produced, and it tends to be easier to remove the organic solvent and water from the curable composition containing the organic solvent and water. The area ratio of A2 is more preferably 40% or less, and further preferably 25% or less. The area of ​​A2, i.e., the content of A2, can be controlled by purification after the oxidation reaction when a hydrosilane compound is oxidized to obtain a cyclic silanol in the production of a curable composition, for example. The area ratio of A2 can be measured by gel permeation chromatography, specifically, by the method described in the Examples.

[0050] The curable composition according to this embodiment can be prepared, for example, by oxidizing a hydrosilane compound in the presence of water or an alcohol. The hydrosilane compound is preferably a hydrogen-containing tetra-substituted tetracyclosiloxane, and a commercially available product may be used.

[0051] The hydrosilane compound is preferably a tetrasubstituted tetracyclosiloxane represented by the following formula (8):

[0052] [ka]

[0053] In formula (8), R has the same definition as R in formula (1).

[0054] Specific examples of the cyclic hydrosilane compound include tetramethyltetracyclosiloxane, etc. Generally, the cyclic hydrosilane compound does not have a hydroxy or alkoxy functional group, but such functional groups may be present in a certain amount before the oxidation reaction.

[0055] Examples of methods for oxidizing a hydrosilane compound include methods using a catalyst and / or an oxidizing agent.

[0056] As the catalyst, for example, a metal catalyst such as Pd, Pt, or Rh can be used. These metal catalysts may be used alone or in combination of two or more. Furthermore, these metal catalysts may be supported on a carrier such as carbon.

[0057] As the oxidizing agent, for example, peroxides can be used. Any peroxides can be used, and examples thereof include oxiranes such as dimethyldioxirane.

[0058] As a method for oxidizing a hydrosilane compound, it is preferable to use Pd / carbon from the viewpoints of reactivity and ease of catalyst removal after the reaction.

[0059] When the tetra-substituted tetracyclosiloxane represented by formula (8) is used as a starting hydrosilane compound and oxidized, the resulting tetrahydroxytetra-substituted tetracyclosiloxane may contain, and preferably consists of, cyclic silanols (B1) to (B4) represented by formulas (2) to (5).

[0060] [ka] [ka] [ka] [ka]

[0061] In the formulas (2) to (5), R has the same definition as R in the formula (1).

[0062] When a metal catalyst is used to oxidize a hydrosilane compound, the catalyst remains in the reaction solution. Therefore, removing the metal by filtration can reduce coloration of the curable composition due to the remaining metal catalyst. Examples of suitable methods include using powdered cellulose as a filter aid in the filtration step. Examples of commercially available powdered cellulose include, but are not limited to, KC Floc W50GK (manufactured by Nippon Paper Industries Co., Ltd.), KC Floc W100-GK (manufactured by Nippon Paper Industries Co., Ltd.), and Cellulose Powder 38 μm (400 mesh) pass-through (manufactured by Wako Pure Chemical Industries Co., Ltd.).

[0063] The curable composition according to this embodiment has a transmittance of 55% or more with respect to light of at least one wavelength selected from the group consisting of wavelengths of 265 nm, 280 nm, and 320 nm, measured in a quartz cell with an optical path length of 10 mm. However, if the cellulose used for filtration is used as it is, the ultraviolet transmittance of the curable composition is low and the storage stability also tends to be poor. This phenomenon is considered to be because impurities present in the cellulose absorb ultraviolet light and also promote polymerization. By sufficiently washing the cellulose with a solvent such as tetrahydrofuran before filtration, a curable composition and a cured product with high ultraviolet transmittance and excellent storage stability can be obtained. The solvent used for washing is preferably a polar solvent such as tetrahydrofuran, diethyl ether, 1,4-dioxane, 1,2-dimethoxyethane, methanol, ethanol, isopropanol, acetonitrile, acetone, methyl ethyl ketone, dimethylformamide, dimethyl sulfoxide, chloroform, dichloromethane, 1,2-dichloroethane, glycerin, ethylene glycol, etc. from the viewpoints of impurity solubility and purification efficiency. The cellulose washing may be carried out either under an inert gas or under air, but it is preferably carried out under an inert gas from the viewpoint of reducing the transmittance due to oxidation of the solvent or the like.

[0064] From the viewpoint of further improving the transmittance of the curable composition according to this embodiment with respect to light of at least one wavelength selected from the group consisting of wavelengths of 265 nm, 280 nm, and 320 nm, it is preferable to distill the raw material hydrosilane compound before oxidizing the raw material hydrosilane compound.

[0065] The cyclic silanol (A1) in this embodiment contains the cyclic silanols (B1) to (B4) represented by the above formulas (2) to (5). When the ratio (mol%) of the cyclic silanol (B2) to the total amount of the cyclic silanols (B1) to (B4) is b, it is preferable to satisfy 0 < b ≤ 20. Examples of the method for setting the ratio b to 0 < b ≤ 20 include a method of combining a recrystallization operation and removal of crystals. When tetramethyltetracyclosiloxane is used as a hydrosilane compound and oxidized, the resulting tetrahydroxytetramethyltetracyclosiloxane 1 When H-NMR is measured, six peaks corresponding to four isomers are observed (here, three peaks are observed for the trans-trans-cis form). The hydrogen atoms in R are observed in the following order from the higher magnetic field side: all-cis (cyclic silanol (B1)), trans-trans-cis (cyclic silanol (B3)), trans-trans-cis (cyclic silanol (B3)), cis-trans-cis (cyclic silanol (B2)), all-trans (cyclic silanol (B4)), and trans-trans-cis (cyclic silanol (B3)). Therefore, the proportions of each of the cyclic silanols (B1) to (B4) are calculated from the integrals of these hydrogen atoms. In this embodiment, the cis and trans forms of the cyclic hydrosilane compound refer to two adjacent hydroxy groups or two adjacent R groups being in the same orientation relative to the cyclic siloxane skeleton (cis) and two adjacent hydroxy groups or two adjacent R groups being in different orientations relative to the cyclic siloxane skeleton (trans), respectively.

[0066] The cyclic silanol (B2) represented by formula (3) is also crystalline, and therefore, when a good solvent is used in the reaction solution, it precipitates as crystals by adding a poor solvent. The cyclic silanol (B2) tends to cause the synthesized cyclic silanol (A1) to become cloudy. This phenomenon is thought to be due to the crystalline nature of the cis-trans-cis cyclic silanol (B2), and is particularly pronounced during storage or when frozen at -60°C. Examples of good solvents include tetrahydrofuran, diethyl ether, acetone, methanol, ethanol, isopropanol, dimethylformamide, dimethyl sulfoxide, glycerin, ethylene glycol, and methyl ethyl ketone. These good solvents may be used alone or in combination. Examples of poor solvents include toluene, chloroform, hexane, dichloromethane, and xylene. These poor solvents may be used alone or in combination.

[0067] As described above, the curable composition according to this embodiment is suitably produced by preparing a cyclic silanol by oxidizing a hydrosilane compound in the presence of water or an alcohol, and then filtering to remove the catalyst and / or oxidizing agent. The curable composition according to this embodiment is preferably produced by adding a poor solvent to a solution containing the product obtained by the synthesis of the cyclic silanol for recrystallization, filtering the solution, and concentrating the solution of the soluble portion obtained by filtration.

[0068] The curable composition according to this embodiment preferably contains the cyclic silanol (A1) and its dehydration condensate (A2) at a concentration of 1% by mass to 99% by mass. The concentration of the cyclic silanol (A1) and its dehydration condensate (A2) in the curable composition according to this embodiment may be 5% by mass to 60% by mass, or 8% by mass to 30% by mass.

[0069] In producing the curable composition according to this embodiment, the solution of the soluble portion may be optionally concentrated, and the solution of the soluble portion itself may be used as the curable composition. Furthermore, since it is not necessary to remove all of the solvent contained in the solution when concentrating the solution of the soluble portion, the curable composition according to this embodiment may be a crude concentrate obtained by distilling off a portion of the solvent contained in the solution of the soluble portion. Furthermore, the curable composition according to this embodiment may be one obtained by concentrating the solution of the soluble portion and then re-diluting it with a solvent or by replacing the solvent used for the soluble portion with a solvent other than that used for the soluble portion. As described above, one preferred aspect of this embodiment is a curable composition containing a solvent.

[0070] The amount of the solvent in the curable composition is not particularly limited, but is preferably 99% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less, based on the total amount of the curable composition. The lower limit of the amount of the solvent is not particularly limited, but may be 1% by mass or more.

[0071] Examples of the solvent in the curable composition include water and / or alcohol used in the reaction, and good and poor solvents used in recrystallization. Specific examples of the solvent include, but are not limited to, water, tetrahydrofuran, diethyl ether, acetone, methanol, ethanol, isopropanol, dimethylformamide, dimethyl sulfoxide, glycerin, ethylene glycol, methyl ethyl ketone, toluene, chloroform, hexane, dichloromethane, and xylene. These solvents may be used alone or in combination of two or more.

[0072] The cured product according to this embodiment is obtained by evaporating the solvent under reduced pressure and then thermally curing the product under an inert gas atmosphere. The temperature during thermal curing is preferably 80°C or higher, more preferably 100°C or higher. The cured product obtained by thermal curing may be further irradiated with light. The R substituent is removed by light irradiation, resulting in a silicated cured product.

[0073] The curable composition and cured product according to this embodiment are used as ultraviolet optical materials, which can be used, for example, as adhesives for hemispherical lenses in ultraviolet light emitting devices. [Example]

[0074] The present invention will be explained in more detail using examples and comparative examples, but the present invention is not limited to these examples in any way.

[0075] The various measurement and evaluation methods are as follows.

[0076] (Calculation of Toluene Concentration in a Solution of Cyclic Silanol (A1) and Its Dehydration Condensate (A2)) Toluene in curable compositions containing cyclic silanol (A1) and its dehydration condensate (A2) according to Examples and Comparative Examples was quantified by the internal standard method under the following conditions using a gas chromatograph (hereinafter also referred to as "GC") 2010Plus manufactured by Shimadzu Corporation. Note that in these Examples, no volatile substances absorbing light at wavelengths of 265 nm to 320 nm were contained other than toluene. 1) Creating a calibration curve An isopropanol solution containing 1% by mass of toluene was prepared. Then, 0.200 g of this solution was taken and 1.800 g of isopropanol was added to obtain an isopropanol solution containing 0.1% by mass of toluene. Using the 0.1% by mass isopropanol solution, an isopropanol solution containing 0.01% by mass of toluene was prepared in the same manner. This procedure was repeated to prepare isopropanol solutions containing 0.001% by mass and 0.0001% by mass (1 ppm) of toluene. 0.010 g of hexadecane was added to 0.120 g of the toluene-containing isopropanol solution obtained above at each concentration, and GC measurement was performed under the following conditions. A calibration curve was then created, with the common logarithm of the area ratio of GC toluene to hexadecane on the x-axis and the common logarithm of the mass ratio of toluene to hexadecane on the y-axis. Under the GC conditions below, the retention time of toluene was 4.0 minutes, and the retention time of hexadecane was 18.4 minutes. 2) Quantification of the Toluene Concentration in the Isopropanol Solution of D4OH and Its Dehydration Condensate 0.200 g of the isopropanol solution of D4OH and its dehydration condensate was filtered using a syringe filter Millex (registered trademark) manufactured by MERCK (hydrophilic polytetrafluoroethylene, pore diameter 0.20 μm, diameter 13 mm φ). Subsequently, 0.150 g of isopropanol and 0.010 g of hexadecane were added to 0.150 g of the filtrate and mixed uniformly. Thereafter, GC measurement was performed under the following conditions, and the toluene was quantified using the calibration curve prepared. <GC Conditions> · Column: DB-1701 manufactured by Agilent Technologies, Inc. (Length: 30.0 m, Inner diameter: 0.25 mm ID, Film thickness: 0.25 μm) · Injection volume: 1.0 μL · Injection temperature: 250 °C · Detection temperature: 350 °C · Temperature programming: Hold at 50 °C for 5 min → Heat at 10 °C / min → 250 °C, Hold for 30 min · CARRIER GAS: Helium, 122 kPa · Column flow rate: 1.65 mL / min · Linear velocity: 36.4 cm / s · Split ratio: 50.0

[0077] ( 1 Calculation of the Concentrations (Unit: Mass %) of the Solutions of Cyclic Silanol (A1) and Its Dehydration Condensate (A2) Using 1H-NMR Measurement Using a nuclear magnetic resonance apparatus ECZ400S manufactured by JEOL Ltd., with a TFH probe as the probe and 1,3,5-tris(trifluoromethyl)benzene (hereinafter also referred to as TFMB) as the internal standard substance, NMR measurement was performed as follows. Using a sample prepared by adding 25.0 mg of TFMB to 250.0 mg of the solution of cyclic silanol (A1) and its dehydration condensate (A2) and then adding 1.0 g of heavy acetone, 1 1H-NM The reference peak of the heavy solvent was set at 2.05 ppm, and the measurement was performed 8 times. The concentrations of the cyclic silanol (A1) and its dehydration condensate (A2) can be approximately calculated by the following formula: Concentration (mass%) of cyclic silanol (A1) and its dehydration condensation product (A2) = 100 - (concentration (mass%) calculated from internal standard substance) The concentration of the solvent can be calculated using the following formula: P s =(S s / S i )×(N i / N s )×(M s / M i )×(m i / m s )×P i P s = Solvent concentration (mass%) P i = TFMB purity (assumed to be 100% by mass) S s =S i The integral ratio of the signal attributed to hydrogen from the solvent (in the case of isopropanol, the region from 0.88 to 1.27 ppm) to S i = Integration value of the signal assigned to hydrogen from the benzene ring of TFMB in the region of 7.54-7.74 ppm (set as 1) N s = number of nuclei in the signal attributed to the solvent (isopropanol = 6) N i = Number of nuclei in the 7.54-7.74 ppm signal attributed to TFMB (=3) M s = molar mass of solvent (isopropanol = 60.01) M i = Molar mass of TFMB (= 282.01) m s =Weight (mg) of a solution of cyclic silanol (A1) and its dehydration condensate (A2) m i =Weight of TFMB (mg)

[0078] (1 Calculation of stereoisomeric ratio of cyclic silanol (A1) using H-NMR measurement NMR measurements were carried out as follows using a nuclear magnetic resonance spectrometer ECZ400S manufactured by JEOL Ltd. and a TFH probe as the probe. A sample prepared by adding 600 μl of deuterated acetone to 100 μl of a solution of cyclic silanol (A1) and its dehydration condensation product (A2) was used. 1 H-NMR was measured. The reference peak of the heavy solvent was set at 2.05 ppm, and the measurement was performed with eight accumulations. When tetramethyltetracyclosiloxane is used as a hydrosilane compound and oxidized, the resulting tetrahydroxytetramethyltetracyclosiloxane 1 In H-NMR, peaks attributable to six types of R bonded to Si, derived from four isomers, were observed in the region of 0.04-0.95 ppm. The hydrogen atoms of the R = methyl group were observed in the following order from the high magnetic field side: all-cis (0.057 ppm), trans-trans-cis (0.064 ppm), trans-trans-cis (0.067 ppm), cis-trans-cis (0.074 ppm), all-trans (0.080 ppm), and trans-trans-cis (0.087 ppm). Using a Delta 5.3.1 (manufactured by JEOL Ltd.), Lorentz transform waveform separation was performed on the peaks assigned to R, and the stereoisomeric proportions of each cyclic silanol were calculated from the peak intensities of these hydrogen atoms.

[0079] (Storage stability) The area percentage of the solution containing the curable composition was measured by GPC, and the (A2) / [(A1) + (A2)] area ratio (%) was calculated. Approximately 1.5 g of the solution containing the curable composition was then placed in a sample bottle, capped, placed in an incubator (Sansho Co., Ltd., small low-temperature incubator SLC-25A), and stored at 25°C for 48 hours. After storage, the area percentages of the cyclic silanol (A1) and dehydration condensate (A2) were measured by GPC, and the (A2) / [(A1) + (A2)] area ratio (%) was calculated. The difference in the (A2) / [(A1) + (A2)] area ratio (%) before and after storage was determined. After storage, an isopropanol solution of the cyclic silanol and its dehydration condensate was dropped onto a polyimide film (Kapton, manufactured by DuPont-Toray Co., Ltd.) and the solvent was evaporated under vacuum at 80°C for 1 hour in a vacuum oven. The atmosphere was then switched to a nitrogen atmosphere, and the material was cured at 100°C for 2 hours to obtain a cured product. The cured product was evaluated after storage by visually inspecting the surface for irregularities.

[0080] (Measurement of Area Percentages of Cyclic Silanol (A1) and Dehydration Condensate (A2) by GPC) 0.1 mL of the solution containing the curable composition was filtered using a syringe filter Millex (registered trademark) manufactured by MERCK (hydrophilic polytetrafluoroethylene, pore size 0.20 μm, diameter 13 mmφ), added to 1.0 mL of stabilizer-free tetrahydrofuran, and mixed well to prepare a measurement sample. This measurement sample was used for measurement using a high-speed GPC device HLC-8420GPC manufactured by Tosoh Corporation. The columns used were TSK guard columns SuperH-H, TSKgel SuperHM-H, TSKgel SuperHM-H, TSKgel SuperH2000, and TSKgel SuperH1000 (all Tosoh Corporation product names) connected in series. The column temperature was set to 40°C, and analysis was performed at a rate of 0.60 ml / min using tetrahydrofuran as the mobile phase. The detector used was an RI (differential refractive index) detector, and SIGMA-Aldrich polymethyl methacrylate standard samples (molecular weight: 2,200,000, 988,000, 608,000, 340,000, 202,000, 88,500, 41,400, 18,700, 9680, 5050, 2380, 800), and separately synthesized D4OH (molecular weight: 304.5), Hexamethylcyclotrisiloxane (Tokyo Chemical Industry, molecular weight: 222.5), Decamethylcyclopentasiloxane (Tokyo Chemical Industry, molecular weight: 370.1) were used as standard substances to determine the number average molecular weight and weight average molecular weight, identify the peaks of p = 0 and p ≧ 1, and calculate the area ratio of the peaks of cyclic silanol (A1) and dehydration condensate (A2).

[0081] (Solution UV-Vis measurement of cyclic silanol (A1) and its dehydration condensation product (A2)) The transmittance of the solution of cyclic silanol (A1) and its dehydration condensate (A2) at 265 nm, 280 nm and 320 nm was measured using a spectrophotometer U-4100 manufactured by Hitachi High-Technologies Corporation. The specific procedure is shown below. A standard quartz cell for spectrophotometers (manufactured by Fluorochemicals) with an optical path length of 10 mm, an optical path width of 10 mm, and material: ES quartz glass was attached to the sample side of the spectrophotometer U-4100, and then a solvent (the same solvent as in the curable composition, in this example, isopropanol) was added to the cell, and the baseline was measured under the following conditions. The sample-side cell was then emptied and washed three times with a solution of cyclic silanol (A1) and its dehydrated condensate (A2) with a toluene concentration of less than 5 ppm. The transmittance of this solution was measured under the following conditions. The average transmittance T (average) of light with wavelengths of 265 to 320 nm was calculated using the following formula:

number

[0082] (UV-Vis measurement of cured product of cyclic silanol (A1)) The transmittance of the cured product of cyclic silanol (A1) at 265 nm, 280 nm and 320 nm was measured using a spectrophotometer U-4100 manufactured by Hitachi High-Technologies Corporation. The specific procedure is shown below. A light-shielding plate with a 10 mm diameter hole was attached to the sample side of the measurement jig of the U-4100 spectrophotometer, and the baseline was measured under the following conditions. A 500 μm-thick cured product of cyclic silanol (A1) was then fixed to the measurement jig using Kapton tape or similar to cover the entire 10 mm diameter hole. The position of the light-shielding plate attached to the jig was always kept constant. Next, after confirming that the transmittance at a wavelength of 800 nm was 95% or higher, the transmittance at a wavelength of 800 nm was set as 100%, and the transmittance of the cured product of cyclic silanol (A1) was measured under the following conditions. <Spectrophotometer conditions> Measurement mode: Wavelength scan Data Mode %T ·Starting wavelength 800.00nm End wavelength 240nm Scan speed 300nm / min Sampling interval: 1.0 nm Initial waiting time 0s Repeat period: 0.0 min Measurement count: 1 Auto-zero before measurement Off Slit 1.50nm Light source switching mode: Automatic switching Light source switching wavelength 340.0nm Baseline setting User 1 D2 lamp On WI lamp On Cell length 10.0nm R / S Inversion Off Light attenuation rate: No light attenuation plate used Photomultiplier voltage Auto 1 ·High resolution measurement Off

[0083] (Film thickness of cured product) The film thickness of the cured product was measured using a constant pressure thickness measuring instrument (JIS standard) PG(J) / PF(J) manufactured by Teclock Corporation.

[0084] [Example 1] (Preparation of Curable Composition) Under an argon atmosphere, 35 g of distilled water, 1100 g of tetrahydrofuran (manufactured by Wako Pure Chemical Industries, Ltd.), and 4.4 g of Pd / C (10% palladium / carbon, manufactured by N.E. Chemcat Corporation) were mixed in a reaction vessel and the temperature of the reaction vessel was maintained at 5°C or below. 1.00 × 102 g of 1,3,5,7-tetramethylcyclotetrasiloxane (Tokyo Kasei, also referred to as D4H) was gradually added to the reaction vessel, and after stirring for 3 hours, 1The reaction was carried out for a total of 20 hours, with 4.4 g of Pd / C (10% palladium / carbon) added in two batches, until the disappearance of the SiH groups was confirmed by H-NMR. The disappearance of the SiH groups was confirmed by the ECZ400S nuclear magnetic resonance spectrometer manufactured by JEOL Ltd., where the reaction solution was dissolved in a 1% by mass concentration deuterated acetone solution. 1 H-NMR was measured and it was confirmed that the SiH groups present at 4 to 5 ppm had disappeared. 93 g of magnesium sulfate was added to the reaction solution, which was then stirred at 5°C or below for 60 minutes to obtain 1,3,5,7-tetrahydroxy-1,3,5,7-tetramethyltetracyclosiloxane (hereinafter also referred to as "D4OH") and its dehydration condensation product. As a filter aid, 400 g of powdered cellulose KC Floc W200G manufactured by Nippon Paper Industries Co., Ltd. was packed using tetrahydrofuran (hereinafter also referred to as THF) and purified. Specifically, 3160 g of THF was poured into the funnel to wash the cellulose. Then, approximately 5 ml of the washing solution was taken and UV-Vis measurement was performed under the above conditions using the THF used for washing as the background, confirming that the transmittance at 265 nm was 95% or more. Next, the reaction solution was passed through the cellulose, and tetrahydrofuran was further poured into the cellulose to obtain 3840 g of a THF solution of D4OH and its dehydration condensate. This solution was concentrated in an evaporator at a water bath temperature of 25°C or less and a rotation speed of 48 rpm until the concentration of D4OH and its dehydration condensate reached 20% by mass, and then transferred to a dropping funnel. It was then added dropwise to a mixed solvent of 1,080 g of toluene and 108 g of tetrahydrofuran over approximately 40 minutes. The dropping funnel was then washed with 88 g of tetrahydrofuran, and the washings were added to the aforementioned dropping mixture. The mixture was stirred at 140 rpm at 0°C or less for 1.5 hours using a stirring blade. The precipitated insoluble matter was then filtered under reduced pressure using Kiriyama filter paper No. 3, φ = 95 mm, and frozen and stored overnight at -60°C. The precipitated insoluble matter was then filtered under reduced pressure again using the same method. A total of 48 g of crystalline solid was recovered from the two filtrations. The filtrate containing the soluble portion (1,840 g) was concentrated under reduced pressure to 827 g of a mixed solution of D4OH and its dehydration condensate in tetrahydrofuran and toluene. If the solution was cloudy, 60 to 400 g of tetrahydrofuran was added to dissolve the insoluble matter, and the mixture was concentrated again under reduced pressure to 827 g of a mixed solution of D4OH and its dehydration condensate in tetrahydrofuran and toluene. Of the 827 g of the tetrahydrofuran and toluene mixed solution of D4OH and its dehydration condensate, 83 g was weighed into a flask and concentrated under reduced pressure to 23 g using an evaporator at a water bath temperature of 25°C or less and a rotation speed of 48 rpm, and then 100 g of isopropanol was added again. Further concentration under reduced pressure was carried out again to obtain 98 g of an isopropanol solution of cyclic silanol (D4OH) and its dehydration condensate (hereinafter also referred to as "IPA solution"). The toluene concentration in this solution was then quantified by GC, and this operation was continued until it was less than 5 ppm. After confirming that the toluene concentration was less than 5 ppm, the concentration of this solution was adjusted using an evaporator so that the concentration of D4OH and its dehydration condensate was 10 mass %, and the concentration was calculated using the above-mentioned NMR method. The amount of toluene used to calculate the stereoisomer ratio of the obtained curable composition was 100 g. 1 The H-NMR spectrum is shown in Figure 1. The obtained isopropanol solution was subjected to the above-mentioned UV-Vis measurement. The isopropanol solution of the D4OH and its dehydration condensate prepared above was dropped onto a polyimide film (Kapton, manufactured by DuPont-Toray Co., Ltd.) and the solvent was evaporated in a vacuum oven at 80°C for 1 hour. The atmosphere was then switched to a nitrogen atmosphere, and the film was cured at 100°C for 2 hours. The cured product was then peeled off to produce a 500 μm-thick cured product. The UV-Vis measurement described above was performed on the resulting cured product. The above-mentioned storage stability test was also carried out using the above-prepared D4OH and its dehydrated condensate in isopropanol. Figure 4 shows a photograph of the surface condition of the cured product after storage.

[0085] [Example 2] D4H was distilled, and the weight ratio of the reagents used was the same as in Example 1, and the experiment was carried out under the same conditions. 1 The H-NMR spectrum is shown in Figure 2. A photograph showing the surface condition of the cured product after storage is shown in Figure 5.

[0086] [Comparative Example 1] The procedure was carried out using D4H with reference to Example 9 of JP 2020-105475 A. In this case, cellulose purification was not performed because this example was followed. 1 The H-NMR spectrum is shown in Figure 2. A photograph showing the surface condition of the cured product after storage is shown in Figure 6.

[0087] [Table 1]

Claims

1. Formula (1): 【Chemical 1】 (in formula (1), each R independently represents a fluorine atom, an aryl group, an alkenyl group, a linear or branched alkyl group having 1 to 4 carbon atoms and substituted with fluorine, or an unsubstituted linear or branched alkyl group having 1 to 4 carbon atoms, and n represents an integer of 2 to 10), and optionally a dehydration condensate (A2) of the cyclic silanol (A1), A curable composition having an average transmittance of 75% or more for light having a wavelength of 265 nm to 320 nm when a solution of the curable composition in which the total amount of the cyclic silanol (A1) and the dehydration condensate (A2) is 10 mass % is measured in a quartz cell having an optical path length of 10 mm.

2. The cyclic silanol (A1) is Formula (10): 【Chemistry 2】 The curable composition according to claim 1, comprising a cyclic silanol (A10) represented by the formula (10): wherein R has the same meaning as R in the formula (1).

3. The cyclic silanol (A10) is Formulas (2) to (5): 【Chemistry 3】 【Chemistry 4】 【Chemistry 5】 【Chemistry 6】 (In the formulas (2) to (5), R has the same meaning as R in the formula (1) above.) The curable composition according to claim 2, wherein b is the proportion (mol %) of the cyclic silanol (B2) relative to the total amount of the cyclic silanols (B1) to (B4), and 0<b≦20 is satisfied.

4. The curable composition according to claim 1 , comprising a dehydration condensate (A2) of the cyclic silanol (A1).

5. 5. The curable composition according to claim 4, wherein, in a peak of a chromatogram obtained by measurement by gel permeation chromatography, an area ratio of the dehydration condensate (A2) to the total area of ​​the cyclic silanol (A1) and the dehydration condensate (A2) is 50% or less.

6. The curable composition according to claim 4, comprising the cyclic silanol (A1) represented by the formula (1) and its dehydration condensate (A2) in a concentration of 1% by mass to 99% by mass.

7. The curable composition according to claim 1, which has a transmittance of 70% or more for light of at least one wavelength selected from the group consisting of 265 nm, 280 nm, and 320 nm.

8. A cured product of the curable composition according to any one of claims 1 to 7, A cured product having a transmittance of 70% or more at a thickness of 500 μm for light of at least one wavelength selected from the group consisting of 265 nm, 280 nm and 320 nm.

9. The cured product according to claim 8, which has a transmittance of 80% or more at a thickness of 500 μm for light of at least one wavelength selected from the group consisting of 265 nm, 280 nm and 320 nm.

10. An ultraviolet optical material, which is the curable composition according to any one of claims 1 to 7, or the cured product according to claim 8 or 9.

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